In color printing, it is often desirable to print black text and barcodes using K-only gray/black ink and/or toner (hereinafter “ink”) in lieu of the process or rich gray/black ink. K-only ink is associated with the CMYK subtractive color model used in color printing. CMYK stands for Cyan, Magenta, Yellow, and Key. The Key stands for black. The cyan, magenta, and yellow colors in the CMYK model are also known as subtractive primaries. The CMYK model works by partially or entirely masking certain colors on a typically white background (that is, absorbing particular wavelengths of light). CMYK utilizes mixtures of the cyan, magenta, and yellow colors and techniques such as half-toning to create a full spectrum of colors for color printing.
The K, or gray/black, of the CMYK model is used to produce deeper black tones, unsaturated colors, and dark colors by substituting for the combination of the subtractive primary colors. Adding the K ink absorbs more light and yields much “blacker” blacks. K-only gray/black is defined by using only the black (K) in the CMYK model, with no cyan, magenta, or yellow colors.
On the other hand, a process (or rich) gray/black may be produced in the CMYK model by adding K ink along with some mixture of each of the subtractive primary inks. However, this mixing of cyan, magenta, and yellow primary colors is typically unsatisfactory for darker tones because it often results in a muddy dark brown color that does not appear quite black. In addition, a combination of a high percentage of cyan, magenta, and yellow inks soaks the paper with ink, making it slower to dry, sometimes impractically so. Finally, finely detailed printing using the three subtractive primary inks without any slight blurring requires impractically accurate registration (i.e., all three images, or colors, would need to be aligned extremely precisely).
As discussed above, process gray/black uses much more ink compared to K-only gray/black ink. As a result, printing gray or black text and barcodes with K-only ink can save ink usage amounts. In addition, text and barcodes printed with process gray/black ink may have color fringe or bleeding due to registration errors and poor plate alignment, which may cause print quality problems such as barcode readability issues. Utilizing K-only printing of text and barcodes can avoid this color fringe problem. As a result, a solution to enforce K-only gray/black printing of text and barcodes in a color printing system would be beneficial.